Photo-electric cell



May 15, 1934. v A. WILLIAMS 1,959,073

PHOTO-ELECTRIC CELL Filed ug. 29, 1933 5 j 5 4 1 Fig. Z

JNKEN'TOR Alberi Leslzelfl/zllzams.

-BY r; n

HIS ATTORNEY Patented May 15, 1934 UNITED STATES PHOTO-ELECTRIC CELLAlbert Leslie Williams, Kings Cross, London, England, assignor, by mesneassignments, to The Union Switch & Signal Company, Swissvale, Pa., acorporation of Pennsylvania Application August 29, 1933, Serial No.687,307 In Great Britain August 17, 1932 1 Claim.

This invention relates to photo-electric cells of the kind comprising aphoto-sensitive element of the dry surface contact type and has for itsobject to provide an improved photo-electric cell of this character.

When a so-called second class conductor such for instance as cuprousoxide is in relatively intimate contact with a conductor such as a metalfor instance copper or gold an electro-motive force is found to begenerated when the combination is subjected to the action of light, thegeneration of electro-motive force being believed to occur at theboundary or contact surface of the two conductors and tending to cause aflow of current from the conductor of lower speciic resistance toV thatof higher specic resistance, for instance from the copper or gold to thecuprous oxide rthrough this boundary or contact surface.

According to the principal feature of the inven tion the cell comprisesa second class conductor or conductor in photo-electric contact withmore than one conductor or second class conductor respectively, the cellbeing responsive to light of different Wave lengths or ranges of wavelengths according to whether the light traverses a second classconductor or not in order to reach the boundary or contact surface atwhich the electromotive force is generated, this conductor being in theform of a relatively thin plate or layer adapted to transmit lightcorresponding to a portion of the spectrum dependent upon the nature ofthe conductor.

According to a further feature of' the invention, the second classconductor is arranged to be in relatively intimate contact over aportion only of one of its surfaces with a conductor of lower specicresistance and in Contact over another portion of its opposite surfacewith a second conductor of lower specic resistance, so that the boundaryor contact surface on one side of the second class conductor is subjectto the action of light transmitted through the portion of the conductorwhich is not in contact with the conductor on the opposite side. Thedirection in which ythe electro-motive force is generated when onesurface of the cellv is exposed to light will thus bediierent for lightof different colors dependent upon which of the two boundary or contactsurfaces receives the light after transmission through the conductor orsecond class conductor.

The invention is illustrated by Way of example in the accompanyingdrawing Figures 1 and 2 of which are views in sectional elevation andplan respectively of one form of photo-sensitive element for aphoto-electric cell embodying the'in- (Cl. 13G-89) vention, the verticaldimensions of the various elements being shown as greatly exaggeratedfor the sake of clearness.

Referring now to the drawing it will be seen that the photo-sensitiveelement consists of a thin plate or disc 1 of copper, the upper face ofwhich is coated with a layer 2 of cuprous oxide preferably formeddirectly thereon by a heating operation. An annular zone of the upperface of the oxide layer 2 is coated with a layer 3 of gold formed bysputtering or in any other suitable manner, the remainder of this faceof the oxide layer 2 being left clear.

The annular zone 3 of applied gold and the copper plate or disc l formthe terminals of the element and assuming that a beam of light isdirected upon the upper face of the element the operation is as follows.

If the light is of a Wave length or lengths corresponding to the red endof the spectrum, the rays of light are intercepted by the layer of gold3 but are transmitted through the thin layer of cuprous oxide 2 over theclear portion of the upper face of the element and pass to the boundaryor contact surface 4 between the oxide 2 and the copper plate or disc 1thereby generating an electro-motive force in adirection tending tocause a low of current within the element from the copper 1 to the oxide2. If however the light is of a Wave length or lengths corresponding tothe green portion of the spectrum, the rays it light are intercepted bythe layer 2 of cuprous oxide over the clear portion of the upper face ofthe element but are transmitted through the layer of gold 3 to theboundary or contact surface 5 between this layer and the layer ofcuprous oxide thereby generating an electro-motive force in a directiontending to cause a ow of current from the gold 3 to the oxide 2, that isto say, in the opposite direction to that corresponding to red light.

It will be observed that the selective action is due to the'fact thatcuprous oxide in the form of a thin nlm is translucent to red light andthat gold in a thin layer is translucent to green light.

The cell is thus responsive to either red or green light and generatesan electro-motive force in one direction or the other according to thecolor of the` light to which it is subjected, and the sensitiveness orresponse of the cell to the different colors may evidently be varied asdesired by varying the relative areas of the annular zone 3 of appliedgold and of the remaining clear portion of the upper face of theelement, or by varying the relative thickness of the layers of gold andcuprous oxide or by both variations.

In addition to the photo-electric action above described, there will ingeneral be a rectifying action at the boundaries or Contact surfaces 4,5 which is dierent for diierent conducting or semi-conducting materialsand the modicaton of the magnitude of the photo-electric effect obtaineddue to the rectifying action may be utilized in adjusting the selectiveresponse of the device as will be understood without furtherexplanation.

It will be understood that other conductors and second class conductorsthan those above mentioned may be utilized having regard to theirphoto-electric properties and translucency to light of different colors.

Although I have herein shown and described only one form ofphoto-electric cell embodying my invention, it is understood thatvarious changes and modifications may be made therein within the scopeof the appended claims Without departingfrom the spirit and scope of myinvention.

Having thus described nur invention, what I claim is:

A device capable of functioning as a generator of electric currentcomprising copper having a layer of cuprous oxide permeable to lightformed thereon and integral therewith, and an uncovered layer of goldpermeable to light in intimate contact with only a portion of the freesurface of said oxide, means for at times supplying to the` freesurfaces of said oxide and said gold light of such Wave length as to betransmitted by the oxide to the junction of the copper and the oxide butto be intercepted by the gold and at other times supplying to said freesurfaces light of such Wave length as to be transmitted by the gold tothe junction of the gold and the oxide but to be intercepted by theoxide, said device being characterized by the fact that when lightstrikes the junction of the copper and the oxide an electric current iscaused to ow across such junction from the copper to the oxide Whereaswhen light strikes the junction of the gold and the oxide an electriccurrent is caused to flow across such junction from the gold to theoxide.

ALBERT LESLIE WILLIAMS.

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